DESCRIPTION(adapted from applicant's abstract): The broad objective of the proposed research is to provide a more detailed understanding of pre-attentive processes that contribute to auditory perception. We will use high temporal resolution of event-related potentials in conjunction with behavioral methods to compare the outcome of pre-attentive auditory processes with the perception resulting from attentive processing of the same sounds, across various experimental conditions. This will allow us to evaluate the processing stages between sensory input and behavioral response. There are three main aims of the proposal. One is to determine the extent of processing of unattended acoustic information. Four experiments address this aim. One tests the pre-attentive processing capacity. Another determines whether the process of auditory feature integration is entirely pre-attentive. A third tests the hypothesis that the auditory system organizes information from multiple unattended sources when attention is directed to a single acoustic source. The fourth investigates stimulus context effect on auditory event formation. A second aim is to understand how attention and pre-attentive processes interact. Two experiments address this aim, one investigates how perception relates to pre-attentive auditory event formation and another characterizes the way in which pre-attentive auditory events can affect behavioral performance. The third aim is to provide further evidence for attentional modulation of early auditory processes. One experiment will test the hypothesis that top-down processing can modify pre-attentive grouping processes. Deficits in central auditory processing are to be key in many cognitive disorders. Using electrophysiological measures, in conjunction with behavioral methods, to delineate the pre-attentive processes that contribute to auditory perception can help advance our understanding of impaired processing, which is essential for developing rehabilitative treatments. Furthermore, because subject response is not needed for measuring the ERP components, this methodology has the potential to be an important noninvasive tool for diagnosis of central auditory processing deficits that contribute to impaired cognition.